With the rapid development of smart phones, new technologies for camera functions of mobile phones are constantly generated. For example, 3D imaging technology, an optical sensing technology based on 3D structured light and provided by Apple Inc, can be used for face or gesture recognition, which improves camera functions, brings new applications of augmented reality (AR) and transforms an optical image from a past two-dimensional image to a three-dimensional image, thus bringing a more real and clear perception experience.
The 3D structured light technology refers to a technology in which specific laser information is projected onto a surface of an object and then is captured by a camera, and information such as position and depth of the object is calculated according to a change of light information caused by the object, so as to reconstruct the entire three-dimensional space. The specific laser information is an important indicator of the 3D structured light technology, and thus requirements for a collimator lens system which projects the laser information onto the surface of the object to be tested are high. Therefore, a collimator lens system projecting point light source array with a specific solid angle on a surface of a vertical cavity surface emitting laser (VCSEL) onto the surface of the object to be tested is a key point of 3D imaging quality.
In the existing collimator lens system products, a focal length of a lens changes greatly with the change of ambient temperature, which results in significant change in an angle of the light projected by the lens, causes the change of the original light information, and further leads to errors in the calculation of the entire system, thus affecting an accuracy of a profile reconstruction of a three-dimensional object. Moreover, image points projected become larger as the ambient temperature changes, which leads to a sharpness reduction of the clarity of a three-dimensional image reconstructed by the system.